Hybrid energy storage devices, also known as asymmetric supercapacitors or hybrid battery/supercapacitors, combine battery electrodes and supercapacitor electrodes to produce devices having a unique set of characteristics including cycle life, power density, energy capacity, fast recharge capability, and a wide range of temperature operability. Hybrid lead-carbon energy storage devices employ lead-acid battery positive electrodes and supercapacitor negative electrodes. See, for example, U.S. Pat. Nos. 6,466,429; 6,628,504; 6,706,079; 7,006,346; and 7,110,242.
The conventional wisdom is that any new battery or supercapacitor technology assembles components and uses techniques that are unique to that technology. Moreover, the conventional wisdom is that lead-carbon energy storage devices are required to be assembled using relatively high compression of the cell or cells within the device. The high compression is due in part to the large contact resistance existing between an activated carbon active material and a current collector of a negative electrode. It is also conventional wisdom that equipment generally used to manufacture conventional lead-acid batteries and commonly employed in the automotive industry, motive power, stationary, and other energy storage applications cannot be employed in the production of hybrid energy storage devices.
The present invention provides a negative electrode for hybrid energy storage devices, which are capable of being manufactured using available conventional lead-acid battery manufacturing equipment. The inventors have proven that single cell and multi-cell hybrid energy storage devices may be manufactured using conventional lead acid-battery manufacturing equipment with modifications. Cast-on equipment may be adapted to handle activated carbon-based negative electrodes in a similar manner to how conventional lead acid battery lead-based negative electrodes are handled.
It is a purpose of the present invention to provide negative electrodes for hybrid energy storage devices, which may be manufactured using easily available and relatively inexpensive conventional lead-acid battery manufacturing equipment. These negative electrodes embody a modified design to reduce the need for large stack pressure and to obtain acceptable electrochemical performance. Accordingly, the negative electrodes are compatible with existing lead-acid battery manufacturing techniques.